Considering China has bought up a majority of gold in the past decade, and they're the global leader in production, I'd say CryptoYuan will have the best chance of winning out.

I assume they're keeping their designs under wraps for now, but I haven't really taken a deep look. There is some info available though:

* The Chinese Central Bank has filed over 80 patents relating to CryptoYuan, which can be checked out - https://digitalchamber.org/pboc-patent-repository/

* The European Central Bank released a report in October - https://www.ecb.europa.eu/pub/pdf/other/Report_on_a_digital_...

* The Federal Reserve is apparently still just researching - https://www.federalreserve.gov/econres/notes/feds-notes/cent...

DDoSing another state's crypto would probably be considered an overt act of war, so I don't know how often that could happen.

I have no idea what Libra is to be honest.